DE102014003801B3 - Flow cell with variable layer thickness - Google Patents

Abstract

The invention describes a process-suitable flow cell for optical applications, which is particularly suitable for microscopic examinations in the context of automated process control. As a special feature, the device allows a pressure-controlled change in the layer thickness. The invention provides a closed container with inlet and outlet in which are mounted on two opposite sides of optical components whose distance from each other can be changed and in this case very small distances can be realized. This makes it possible for a flushing to increase the distance between the two optical components and to reduce the distance between the two optical components for an optical measurement. The change in the layer thickness is made possible by the use of an elastically deformable component whose deformation can be controlled in a particularly simple manner by applying an overpressure or underpressure inside or outside the cuvette.

Description

The invention relates to a process-flow cuvette for optical applications, which is particularly suitable for microscopic examinations in the context of automated process control. The device allows a pressure-controlled change in the layer thickness.

State of the art:

In order to be able to examine a sample by means of a microscope, it is generally necessary to apply the sample liquid to a microscope slide (OT) and flatten it with a coverslip (DG). Flattening serves the purpose of moving the sample holistically into the focal plane of the objective, while minimizing the thickness of the layer serves the purpose of preventing objects from lying behind the focal plane of the objective. This would adversely affect the image quality, or the then only insufficient optical exposure could cause problems in the electronic image processing.

The process of sampling, applying to a TDC, placing a DG, and attaching it to a microscope stage causes work and requires a significant time lag between the moment of sampling and the presence of an evaluable image. For use in the context of automated process control, this manual method of microscopy is insufficiently suitable.

Further, in the conventional method, it can not be excluded that the sample is temporarily in contact with the atmosphere. This creates the risk of sample contamination or reaction with atmospheric oxygen.

If the sample has harmful properties, the open handling of it is also a disadvantage. In addition, the staff may need to be specially trained for a manual handling of a particular substance.

Once the microscopic evaluation is complete, it is usually necessary to dispose of the specimen; it is usually not possible to return the sample to the process. This not only represents a further step, especially with regard to toxic, carcinogenic, corrosive or flammable samples, etc. may well incurred considerable costs for disposal.

task

Description of the invention:

The object of the present invention is to avoid the disadvantages mentioned, to ensure unrestricted process capability and, moreover, to enable as simple and practical handling as possible while at the same time achieving low production costs.

In addition to the use of the cuvette in the field of application of microscopy (eg transmitted light, incident light, dark field, or phase contrast) is also a use in other areas of measurement, for example, the spectroscopy of highly absorbent samples as an alternative to the ATR principle (attenuated total reflection) , thought.

The invention provides a closed container with inlet and outlet, in which on two opposite sides of optical components, hereinafter referred to as windows, are mounted, the distance can be changed by a mechanism and in particular very small distances can be realized. This makes it possible to radiate light from one or both sides of the sample located in the interior and at the same time on one or both sides by means of a suitable optics, for. B. a commercially available lens, an image tap.

Since a small layer thickness is necessary for taking a sharp image, as mentioned at the outset, the container must be designed so that the two opposite windows have only a small distance. A small distance in this sense could be between z. B. one and 100 microns, advantageously between one and 20 microns and more preferably between one and 5 microns.

However, the requirement for the smallest possible layer thickness is in conflict with a good flow through the cavity, since small flow cross sections are known to be associated with a high pressure drop.

The invention now provides, for the time of flushing to be able to increase the distance between the two windows. This is achieved by one of the two windows is movably mounted and its position can be changed by a force application. Ideally, the window used as OT is movably supported while the window used as DG is in a fixed position. However, in other embodiments, the positions could also be reversed. In the first case it is ensured that the distance from DG to lens does not change and thus the focal plane does not lose its position. Since the distance to the DG is very low, in particular with strongly magnifying lenses, the maximization of the layer thickness would also have narrow limits. If an immersion medium is used to improve the optical imaging or another purpose, it is also advantageous to make the position of the DG immobile to the lens, otherwise the immersion medium could be pushed away after various movement processes.

To realize the movable and at the same time dense window storage, the present invention provides in one embodiment an elastically deformable component in which z. B. a viewing window is used in the middle. This component, hereinafter referred to as membrane, z. B. consist of a sheet, which is optionally provided to increase the elasticity with an imprint. Also possible is the use of an elastomer or polymer as the membrane material.

The introduction of the viewing window in the membrane can be done by gluing, screws, clamps or other technology conventional technology. If appropriate, the viewing window or windows can also be designed as a polarizing filter, diffusing screen or other optical component; it does not necessarily have to be a transparent pane.

If, in one embodiment, the membrane is made of a transparent material, it may also be possible to dispense with a separate pane. The membrane serves in this case simultaneously as a viewing window. The simplest possibility of the technical implementation is the use of a film-like material. If higher demands are placed on the area used as TDC, the design of the membrane / viewing window component as an injection molded part is appropriate, in which the flexible membrane part is correspondingly thin and therefore flexibly modeled and the middle part serving as a viewing window thicker, more stable and with particular attention to a smooth and clean surface is designed.

In patent specification [ DE10148210 ] describes a flow cell for microscopic applications in which the underside serving as OT is a transparent foil. The said patent, however, aims only at the lowest possible production costs and not at a variability of the layer thickness.

Notwithstanding the patents DE2844004 ], [ DE1918002 ] and [ DE2853703 ], the present invention is not aimed at a manually or motor-controlled change in the layer thickness by means of cylinder / piston principle, but the layer thickness is varied by means of a deformable membrane in a particularly simple manner by a pressure change.

The present invention is likewise based on that in [ DE69910006 ] described in which a layer thickness change by a horizontal displacement of the cuvette shell in conjunction with a sliding seal.

• 1) Ohne Kraftbeaufschlagung befinden sich beide Scheiben in Spülstellung, Schichtdicke ist maximiert. Durch Anlegen eines Unterdrucks wird der beweglich gelagerte OT an das DG gesaugt.
• 2) Ohne Kraftbeaufschlagung befinden sich beide Scheiben in Messstellung, Schichtdicke ist minimiert. Durch Anlegen eines Überdrucks wird der beweglich gelagerte OT vom DG weggedrückt.

The cuvette can be realized in two different versions:

• 1) Without applying force, both discs are in flushing position, layer thickness is maximized. By applying a negative pressure, the movably mounted TDC is sucked to the DG.
• 2) Without applying force both discs are in measuring position, layer thickness is minimized. By applying an overpressure, the movably mounted TDC is pushed away from the DG.

A noteworthy advantage of the first variant is that with a measuring position generated by negative pressure, ie with a minimum layer thickness, the DG presses against the TDC with the same force as the TDC against the DG. It establishes a stable state in which the DG and OT rest flat against each other and are in no way bent or arched, a risk of breakage can thus be ruled out. This is of particular importance in view of the low thickness of the DG in microscopic applications. This is often less than 1 mm, especially for magnifying lenses (commercially available microscope objectives are usually corrected for a cover glass thickness of 0.17 mm with refractive index n = 1.5255).

If a vacuum is applied in the cuvette and both viewing windows move toward one another, the decreasing layer thickness leads to an increase in the pressure loss during the passage of the medium located between the viewing windows. This leads to a decreasing layer thickness to a steady slowing of the disc movement until it practically comes to a halt depending on the applied negative pressure and the viscosity of the medium. For aqueous media and a moderate negative pressure in the range of a few millibar, layer thicknesses of one micrometer can be achieved within seconds without any problems.

If deviating layer thicknesses are of interest, these can be realized by introducing a separate spacer. Also possible for this is the introduction of a bag with a defined depth in one of the two viewing windows.

In order to optimize the movement towards the measuring position, it is crucial that the contact surface between OT and DG is kept as small as possible. This is achieved by that At least one of the two viewing windows is designed as small as possible, limiting factors here are the size of the lens as well as the requirements of the lighting.

Further improvement of the liquid removal can be achieved by the introduction of recessed channels in at least one of the two viewing windows. These channels are to be designed so that the observed object field is not affected. A similar reaction is for example in [ DE1648917 ], where, however, the gutters do not serve to optimize a layer thickness change, but are used only in a cuvette with an invariable layer thickness.

For example, the flow can be throttled for the pressure change necessary for the layer thickness changeover, which leads to an overpressure in the interior of the cuvette at a top feed, for example by opening a valve. If the drain is downwards, a negative pressure can be generated in the interior of the device by means of a suspended liquid column located therein.

To enable completely actuator-free operation, the cuvette can also be structurally combined with a lifting mechanism. In this way, a continuous inflow into a periodic changeover from rinsing to measuring position and back can be realized.

If, for example, due to unfavorable space conditions on the test set-up, it is not possible to use a standpipe or downpipe, pressure control is of course also possible by means of pumps.

The cuvette thus described ensures by its closed structure that neither sample liquid can get into the environment, nor impurities (dust, spores, bacteria, etc.) can get into the sample. As a result, the present invention is ideally suited for bypass operation. When the optical evaluation of the sample in the cuvette is complete, the substance can be recycled to the running process.

In order to prevent wrinkling of the membrane a drape, it is beneficial in certain applications to design the membrane rotationally symmetrical. The round membrane shape also favors a round cuvette geometry, which allows the manufacturing process of turning and thus means a minimum cost of manufacturing compared to other machining processes.

• 1) Metalllegierungen
• 2) Kunststoffe
• 3) Keramische Werkstoffe
• 4) Glas

In order to meet special requirements in terms of corrosion resistance, thermal conductivity, electrical conductivity, etc., the cuvette can be made of a wide variety of materials. The most obvious ones are:

• 1) metal alloys
• 2) plastics
• 3) Ceramic materials
• 4) glass

With a suitable choice of the cuvette, membrane and Sichtfenstermaterials complete food authenticity can be ensured, which allows the use of the cuvette according to the invention in particular in the food and pharmaceutical industries.

Also on the possibility of free choice of material cuvette according to the invention can be designed without restrictions for sterilization by autoclave.

In addition to screws or clamps, a secure cohesion of the components can also be ensured by the use of a bayonet-type closure.

embodiment

Detailed description of the invention:

An embodiment of the cuvette according to the invention will now be described by way of example with reference to drawings. It shows

1 exploded view

2 Section view in flushing position

3 Section view in measuring position

According to 1 the cuvette is divided into three main components, lid 1 , Middle part 2 and bottom part 3 ,

A round window 5 , used in this case as OT, is provided on its lateral surface with a circumferential groove, in which a perforated membrane 4 can be inserted. The groove of 5 is a little thinner than the membrane 4 is thick. The membrane in this case consists of an elastomer. Due to the resulting clamping effect a tightness of both components is guaranteed to each other.

The membrane 4 with inserted window 5 so gets into the bottom part 3 inserted that the membrane over the entire surface in a recess of bottom part 3 lies. If this is the case, the viewing window is located 5 circulating around the edge in another recess of 3 , in the middle of which there is a through-hole. This through-hole serves in this example as an opening for the illumination of the sample.

Will the middle part 2 on 3 Hanging up, one of them wrote 2 provided circumferential rib against the thus clamped membrane from.

The middle part 2 has three circular pockets on the top with through holes arranged concentrically to them. The two eccentrically arranged pockets serve to accommodate two perforated flat gaskets 8th on the turn two spouts 7 be put on. In the concentric pocket is a between two flat gaskets 9 viewing window 6 used. The viewing window 6 in this case serves as DG.

The lid 1 pushes the two spouts 7 on the seals 8th and thus seals against the middle part 2 from. At the same time, a circumferential groove presses against the lid 1 the viewing window 6 with the two seals 9 and thus ensures complete sealing of the cuvette.

The cuvette composed as described is in 2 and 3 shown in sectional view. In 2 the membrane lies flat on the bottom part 3 , The layer thickness is maximized and the area between the two viewing windows 5 and 6 can be rinsed well. This membrane position results when the internal pressure of the cuvette is equal to or higher than the atmospheric pressure.

3 shows the cuvette in the measuring position, ie in the position of the minimum layer thickness. This membrane position occurs when the internal pressure of the cuvette is lower than the atmospheric pressure.

LIST OF REFERENCE NUMBERS

1

cover

2

midsection

3

the bottom part

4

membrane

5

window

6

window

7

spout

8th

gasket

9

gasket

Claims (8)

Flow cell suitable for the examination of liquid samples, comprising two opposite optical or other components, at least one of which is supported in an elastically deformable component such that the position or the relative distance to the respective other component can be changed by deformation of the holding component. Flow cell according to claim 1, characterized in that the distance of the limiting components to each other can be varied without requiring additional components such. B. sliding seals or the like must be used and still the sealing effect is maintained. Flow cell according to one of the preceding claims, characterized in that the deformation of the holding member can be controlled by the generation of an overpressure or underpressure inside or outside of the cuvette. Flow cell according to one of the preceding claims, characterized in that the distance between the two opposing optical components between one millimeter and one micrometer, preferably between 0.8 millimeters and 2 micrometers can be varied. Flow cell according to one of the preceding claims, characterized in that one or both optical components can be made so thin that a use of conventional (microscope) lenses is possible. Flow cell according to one of the preceding claims, characterized in that one of the components can be held stationary in order to keep the distance to a (microscope) objective constant and thus to reliably achieve an optical image. Method for changing the layer thickness of a flow cell according to one of claims 1 to 6, characterized in that the required for the layer thickness control overpressure or underpressure can be generated by standing or hanging liquid columns in the region of the inlet or outlet. A method for changing the layer thickness of a flow cell according to one of claims 1 to 6, characterized in that a change between measuring and flushing position by standing or hanging liquid columns in the inlet or outlet can be achieved (lift principle).

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